Orbital cellulitis pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Tarek Nafee, M.D. [2]
Overview
Pathogenesis
Orbital cellulitis occurs secondary to microbial infiltration of the deep soft tissue cells surrounding the eye, behind the orbital septum.[1] Damage to the cells triggers an acute inflammatory response resulting in vasodilation, increased vascular permeability, and induction of a cascade of inflammatory markers and white blood cell chemoattractants.[2]
Extension of adjacent infection
Orbital cellulitis may spread from direct extension of acute or chronic adjacent infections. This is due to the fragility of the medial and inferior orbital walls, the presence of natural foramina and defects in these structures, and the medial check ligaments extending from extraocular structures and muscle sheaths to the thin medial orbital wall, which separates the orbital cavity from the paranasal sinuses. Some infections that may affect these structures include:[1][3][4]
- Rhinosinusitis (Ethmoid sinusitis and pansinusitis)
- Dacryocystitis, Dacryoadenitis
- Panophthalmitis
- Infected tumour
- Otitis media
- Mucormycosis
- Dental abscess
Direct Inoculation
Traumatic Inoculation
Orbital cellulitis may occur as a result of microbial inoculation to the orbital space due to trauma. Examples of this include:[1]
- Fracture
- Penetration by a foreign body
Iatrogenic Inoculation
Orbital cellulitis may also occur as a result of direct inoculation during surgical procedures such as:[1][3]
- Ocular or periocular surgeries
- Paranasal sinus surgeries
- Other ENT surgeries
Hematogeneous Seeding
In some cases, infections from a distant source may seed to the retroseptal orbital soft tissue by means of hematogeneous spread in patients with bacteremia. This highly vascularized space, coupled with a valveless inferior ophthalmic vein have been implicated in facilitating this mode of infection.[1][3][5]
Associated Conditions
The following conditions are associated with orbital cellulitis:[3]
- Chronic Sinusitis
- Upper respiratory tract infection
- Subperiosteal abscess
Gross and Microscopic Pathology
The following are gross and microscopic images associated with rheumatic fever:
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Orbital cellulitis in the left eye of a child
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Bilateral orbital cellulitis gross pathology
Microscopic Pathology
- Staphylococcus aureus, is a gram-positive bacterium which is the most common of staph infections. Staphylococcus aureus infection can spread to the orbit from the skin. Staph organisms are able to produce toxins which promote their virulence which leads to the inflammatory response seen in orbital cellulitis. Staphylococcus infections are identified by a cluster arrangement on gram stain. Staphylococcus aureus forms large yellow colonies (which is distinct from other Staph infections such as Staphylococcus epidermis which forms white colonies).
- Streptococcus pneumoniae, is also a gram-positive bacterium responsible for orbital cellulitis due to its ability to infect the sinuses (sinusitis). Strep organisms are able to determine their own virulence and can invade surrounding tissues causing an inflammatory response seen in orbital cellulitis (similar to Staphyloccoccus aureus). Streptococcal infections are identified on culture by their formation of pairs or chains. Streptococcus pneumoniae produce green (alpha) hemolysis, or partial reduction of red blood cell hemoglobin.
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Hasanee K, Sharma S (2004). "Ophthaproblem. Orbital cellulitis". Can Fam Physician. 50: 359, 365, 367. PMC 2214559. PMID 15318671.
- ↑ U.S. National Library of Medicine Medlineplus(2014) https://medlineplus.gov/ency/article/000821.htm
- ↑ 3.0 3.1 3.2 3.3 Chaudhry IA, Al-Rashed W, Arat YO (2012). "The hot orbit: orbital cellulitis". Middle East Afr J Ophthalmol. 19 (1): 34–42. doi:10.4103/0974-9233.92114. PMC 3277022. PMID 22346113.
- ↑ Turvey TA, Golden BA (2012). "Orbital anatomy for the surgeon". Oral Maxillofac Surg Clin North Am. 24 (4): 525–36. doi:10.1016/j.coms.2012.08.003. PMC 3566239. PMID 23107426.
- ↑ Zhang J, Stringer MD (2010). "Ophthalmic and facial veins are not valveless". Clin Experiment Ophthalmol. 38 (5): 502–10. doi:10.1111/j.1442-9071.2010.02325.x. PMID 20491800.